Seems the 6500EX is no longer in production? I have 2 presently in service and attempting to buy a spare for backup. New units seem discontinued. Have these gone the way of the dinosaur? Should I wait and move to 6000XP's? The 6500's power output is just right though, would need 3 of the XP's. I suppose my ultimate question is the longevity of the 6500EX...We're full house off grid and need reliability, and my system is only 4 months old.